In contrast to previous studies looking at extreme forms of obesity, this research focused on common childhood obesity, said Dr Struan Grant, study author and Associate Director at the Center for Applied Genomics at The Children's Hospital of Philadelphia.
Obesity is unlikely to be caused purely by genetics, but the presence of these two gene variants, which Dr Grant says are 'very common in the population', may increase the likelihood of becoming obese in the early years of life. He suggests the alterations may function in the intestinal tract and influencing the activity of natural bacteria.
The study, published in Nature Genetics, combined data from 14 studies conducted in the USA, Canada, Australia and Europe. In total, the genomes of 5,530 obese children and 8,318 non-obese controls were analysed.
They identified two variants - one near a gene on chromosome 13, and one near a gene on chromosome 17.
'Certain kids, even in the best environments, are prone to be obese because of genetics. Actually identifying the genes really helps', said Karen Winer, of the Eunice Kennedy Shriver National Institute of Child Health and Human Development in an interview with Time Healthland.
However, the gene variants are not guaranteed to make a child obese; while they may increase the risk, weight gain is still thought to be largely due to environmental factors. As such, researchers advise that a healthy lifestyle, exercising and eating the right foods is still the best way to avoid obesity.